1. Field of the Disclosure
The present disclosure is directed in general to communication systems and, more specifically, to systems and methods for dynamic selection of antennas in wireless devices based on the near field environmental effects, especially hand position of a user.
2. Description of the Related Art
With the development of new communication standards and services, new radio access technologies (RAT) have been developed to support multiple application and services in a single wireless device. Each RAT can use single or multiple antennas and also an antenna can be shared between multiple RATs and support multiple frequency bands. When two or more antennas are used for a single RAT, the device can operate in several modes including diversity, beam-forming and multiple input multiple output (MIMO).
The performance of an antenna in a wireless device is affected by its near field environment, for example nearby objects. This includes the user of the wireless device. When the wireless device is utilized in the proximity of the user, due to the dielectric loading effect of the human tissue, the performance of the antenna is degraded. In particular, when the user holds the device in such a way that the hand or the finger is masking the antenna, the performance is degraded significantly. To prevent this issue as much as possible and provide better coverage, it is desired to locate the antenna at the top or bottom edge of the device. Although with this placement, the problem of antenna masking by human hand is reduced, but there exists EMI issues due to the close proximity of the antenna to the audio circuits, which is a serious challenge in obtaining the required RF characteristics. Also, since the location of antennas is driven by mechanical requirements and customer desired device form factor, the multiple antennas in the device can be placed anywhere in the device based on these constraints. Therefore, it might not always be possible to locate the antenna in the optimum place in terms of radiation performance.
The effect of the user's head, hand, and other environmental parameters affecting antenna performance, depend on the scenario that the device is used, for example typing, phone call, etc. In addition, there might be new requirements imposed by FCC on handset makers on complying with SAR in user's hand. Also, in multi standard devices, multiple RATs may operate simultaneously, which can affect the performance of an antenna, whether it is used as a shared antenna between two or more RATs or utilized for one RAT.
To overcome the above issues, antenna systems are desired which use multiple antennas for a single RAT and there is a freedom on using the optimum antenna among the multiple ones for operation in a given use case scenario. For example plurality of antennas can be placed on the periphery of the circuit board to save space, provide diversity operation or be used in MIMO configuration for LTE and other new wireless standards. Multiple antennas can also be located in other places on the device or on the circuit board. The antennas can be dual or multiband antennas to support multiple RATs.